If you open/edit the dtsx (in say notepad++) and then search for <DTS:Variables> you can take that entire section. You'll need to do reformating to make it work nicely in Excel.

Alternatively, you could write a little script task that looks at the current package and iterates through the variables and writes them to a text file. Only potential issue is not having the task in a scope that let's it see all the variables in the package.